I'm considering the beta decay of a neutron into a proton an electron and an antineutrino. I heard that this was observed in 1957 in Cobalt 60. I don't really understand when the antineutrino comes into action... The experimental results say that they detected more electrons in the direction opposite to the neutron spin. I understand that if parity was to be respected they should have got the same number of electrons in the direction of the neutron spin and in the opposite direction, but in what way is this related to the antineutrino? If you consider an illustration like the one on this page: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/parity.html And you visualize the action of parity like a reflection by a plane perpendicular to the neutron's spin axis, the spin is reversed and the electrons linear momentum is reversed too, but what happens to the anti-neutrinos? Any help greatly appreciated.